patch, 2 partsMake some functions thread-safe

Here are two patches which makes xmalloc, xrealloc and sha1_to_hex thread-safe.

I think the xmalloc/xrealloc patch is a clear improvement compared to the current situation.

The sha1_to_hex patch is a bit complicated and is more of an RFC. It makes use of pthread_once which is not (yet) implemented in our pthreads win32 compatibility layer.

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Fredrik Kuivinen (2):
      Make sha1_to_hex thread-safe
      Make xmalloc and xrealloc thread-safe

 builtin/grep.c         |    2 +-
 builtin/pack-objects.c |    4 ++--
 git-compat-util.h      |    8 +++++++
 hex.c                  |   53 ++++++++++++++++++++++++++++++++++++++++++++++++
 preload-index.c        |    2 +-
 run-command.c          |    3 ++-
 wrapper.c              |   22 ++++++++++++++------
 7 files changed, 83 insertions(+), 11 deletions(-)